scudo: Don't define mallinfo2 on Android.

[pcc]

Summary

On Android, mallinfo2 is an alias of mallinfo, which results
in errors if we try to define both.

[Chia-hungDuan]

Just curious, why we didn't have issue before? I thought it may be fine because it's defined as WEAK ?!

[pcc]

How do you usually build Scudo? When I run the unit tests I cross compile it for Android using llvm's gn build system. If you're building it as part of the Android platform, SCUDO_PREFIX will be defined to add a prefix of scudo_, so the alias in malloc.h wouldn't affect the definitions.

[cferris]

Is it worth examining how we do this on Android? For example, should we remove the mallinfo2 alias for mallinfo, so that we don't have to make this change?

[pcc]

In D146324#4203219, @cferris wrote:

Is it worth examining how we do this on Android? For example, should we remove the mallinfo2 alias for mallinfo, so that we don't have to make this change?

If you removed the mallinfo2 alias and added a definition of mallinfo2 to Bionic, then it would mean that newer NDK versions will increase the API level requirement for mallinfo2 from baseline to whichever version of Android you added it in. So from an NDK user perspective, that doesn't seem like a good idea.

[cferris]

Good point.

LGTM then.

[Chia-hungDuan]

In D146324#4203093, @pcc wrote:

How do you usually build Scudo? When I run the unit tests I cross compile it for Android using llvm's gn build system. If you're building it as part of the Android platform, SCUDO_PREFIX will be defined to add a prefix of scudo_, so the alias in malloc.h wouldn't affect the definitions.

I see, thanks!

That prefix is only added when #if SCUDO_ANDROID && _BIONIC (code), do you think we need to do #if !SCUDO_ANDROID || !_BIONIC?

[pcc]

In D146324#4203326, @Chia-hungDuan wrote:

In D146324#4203093, @pcc wrote:

How do you usually build Scudo? When I run the unit tests I cross compile it for Android using llvm's gn build system. If you're building it as part of the Android platform, SCUDO_PREFIX will be defined to add a prefix of scudo_, so the alias in malloc.h wouldn't affect the definitions.

I see, thanks!

That prefix is only added when #if SCUDO_ANDROID && _BIONIC (code), do you think we need to do #if !SCUDO_ANDROID || !_BIONIC?

That shouldn't be necessary, we aren't using scudo_mallinfo2 on the platform side.

compiler-rt/lib/scudo/standalone/wrappers_c.inc

INTERFACE WEAK struct SCUDO_MALLINFO SCUDO_PREFIX(mallinfo)(void) {
   // Total allocated space (bytes)
   Info.uordblks =
       static_cast<__scudo_mallinfo_data_t>(Stats[scudo::StatAllocated]);
   // Total free space (bytes)
   Info.fordblks = Info.fsmblks;
   return Info;
 }
 
+// On Android, mallinfo2 is an alias of mallinfo, so don't define both.
+#if !SCUDO_ANDROID
 INTERFACE WEAK struct __scudo_mallinfo2 SCUDO_PREFIX(mallinfo2)(void) {
   struct __scudo_mallinfo2 Info = {};
   scudo::StatCounters Stats;
   SCUDO_ALLOCATOR.getStats(Stats);
   // Space allocated in mmapped regions (bytes)
   Info.hblkhd = Stats[scudo::StatMapped];
   // Maximum total allocated space (bytes)
   Info.usmblks = Info.hblkhd;
   // Space in freed fastbin blocks (bytes)
   Info.fsmblks = Stats[scudo::StatFree];
   // Total allocated space (bytes)
   Info.uordblks = Stats[scudo::StatAllocated];
   // Total free space (bytes)
   Info.fordblks = Info.fsmblks;
   return Info;
 }
+#endif
 
 INTERFACE WEAK void *SCUDO_PREFIX(malloc)(size_t size) {
   return scudo::setErrnoOnNull(SCUDO_ALLOCATOR.allocate(
       size, scudo::Chunk::Origin::Malloc, SCUDO_MALLOC_ALIGNMENT));
 }
 
 #if SCUDO_ANDROID
 INTERFACE WEAK size_t SCUDO_PREFIX(malloc_usable_size)(const void *ptr) {